A terrorism investigation resulted in several arrests in San Diego and Minneapolis on Sunday, federal officials confirmed.

The FBI’s Joint Terrorism Task Force and agents from the San Diego field office “executed arrest and search warrants with respect to several individuals,” the FBI told the Los Angeles Times in an email.

“There is no threat to public safety,” said Ben Petok, a spokesman for U.S. Atty. Andrew Luger in Minneapolis.

Relatives of those arrested said the FBI is holding six men, according to Minnesota Public Radio, which first reported on the operation. At least three of those men were the sons of Somali women, MPR reported, and the families said they did not know why the men had been arrested.

Further information about Sunday’s arrests will be provided Monday morning at a Minneapolis news conference, Petok said.

In 2013, four Somali nationals in San Diego, including an imam at a local mosque, were sentenced to prison after being convicted of attempting to aid the Shabab terror group in their homeland. The four raised $8,500, according to court documents. They were sentenced to terms ranging from six to 18 years.